x86/mm, kexec, ima: Use memblock_free_late() from ima_free_kexec_buffer()

The code calling ima_free_kexec_buffer() runs long after the memblock
allocator has already been torn down, potentially resulting in a use
after free in memblock_isolate_range().

With KASAN or KFENCE, this use after free will result in a BUG
from the idle task, and a subsequent kernel panic.

Switch ima_free_kexec_buffer() over to memblock_free_late() to avoid
that bug.

Fixes: fee3ff99bc67 ("powerpc: Move arch independent ima kexec functions to drivers/of/kexec.c")
Suggested-by: Mike Rappoport <rppt@kernel.org>
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230817135558.67274c83@imladris.surriel.com

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index b9145a6..b098b1f 100644 (file)
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -358,15 +358,11 @@ static void __init add_early_ima_buffer(u64 phys_addr)
 #if defined(CONFIG_HAVE_IMA_KEXEC) && !defined(CONFIG_OF_FLATTREE)
 int __init ima_free_kexec_buffer(void)
 {
-       int rc;
-
        if (!ima_kexec_buffer_size)
                return -ENOENT;
 
-       rc = memblock_phys_free(ima_kexec_buffer_phys,
-                               ima_kexec_buffer_size);
-       if (rc)
-               return rc;
+       memblock_free_late(ima_kexec_buffer_phys,
+                          ima_kexec_buffer_size);
 
        ima_kexec_buffer_phys = 0;
        ima_kexec_buffer_size = 0;